1. Field of the Invention
The present invention relates to a centrifugal dryer and a semiconductor manufacturing apparatus, and more particularly, to a centrifugal dryer having a function to detect an elastic wave generating upon striking to a wall of a chamber of a chip produced by breakage of a substrate during a high speed rotation processing therefor to announce an anomaly, and to a semiconductor manufacturing apparatus equipped with said elastic wave detection system.
2. Description of the Background Art
There has been available an wet treatment apparatus as an apparatus performing removal of foreign matter attached on a substrate or a surface layer treatment with a sulfuric acid solution or a hydrogen peroxide solution in a semiconductor manufacturing process. After a treatment for the substrate with the wet treatment apparatus, a centrifugal dryer as one means drying the substrate has been widely used.
The centrifugal dryer rotates the substrate at high speed to remove residual liquid attached on the substrate and transports the stabilized substrate, thereby preventing liquid contamination in the next step.
However, since substrates are rotated at high speed, a substrate has a chance of breakage during the high speed rotation if a wound has been caused on the substrate, for example. Because of the breakage, not only do some other substrates receive damages, but some other substrates also receive wounds by residual chips thereon, which have imposed great inconvenience on semiconductor production.
In order to solve this problem, there have been available centrifugal dryers: one having means detecting an anomaly sound generating when a substrate is broken during a drying processing with a microphone and the other having anomaly sound detection means and vibration detection means detecting vibrations generating upon striking of a chip to a chamber wall, as disclosed in Japanese Patent Laying-Open No. 2000-353684, Japanese Patent Laying-Open No. 2000-353685 and Japanese Patent Laying-Open No. 11-121430(1999).
In cases where an acoustic sensor such as a microphone and a vibration sensor as the vibration detection means, as described above, are adopted, the use has entailed following problem.
When an anomaly sound and an anomaly vibration generate upon striking of a chip, to a chamber wall, produced by breakage of a substrate, the anomaly sound is collected by an acoustic sensor mounted to an exhaust port cylinder or the like, and if a signal amplified by an amplifier exceeds a reference level set in advance, the signal is determined as an anomaly sound.
On the other hand, a vibrational wave generating upon striking of a chip produced by breakage of a substrate to a chamber wall or the like is detected by a vibration sensor provided on a chamber. The vibration sensor amplifies a voltage generated in a piezoelectric element by a vibrational wave at a prescribed amplification factor to output a voltage proportional to the time integral of an input voltage and to output a voltage proportional to a magnitude of an acceleration of a vibration, that is a voltage proportional to a magnitude of a speed of a vibration obtained by time integration of the acceleration.
Anomaly signals of an acoustic wave and a vibrational wave are detected by a sound-vibration detection section, for example, and determination and control are executed by a microcomputer. An anomaly vibration and an anomaly sound are discriminated through the determination and control.
Since the acoustic wave is, however, transmitted through the air, not only is a breakage sound of a substrate generating in a processing chamber collected, but various noises such as a rotation sound of a motor, a sound of opening/closing of a cover, a strainer sound and others are also collected.
If a centrifugal dryer is installed in a space under an environmental condition of silence, an acoustic wave associated with a breakage of a substrate can also be collected, but it cannot be guaranteed that generation of an acoustic wave of a like frequency in the vicinity of the breakage is always absent. Furthermore, even if a by-pass filter is provided in series with a circuit to limit a frequency to a specific one, there is still a fear to cause a wrong detection with respect to an anomaly sound.
Besides, since an installment place of an acoustic sensor is necessary to be selected in a processing chamber or inside an exhaust port cylinder in order to reduce a chance of wrong detection, difficulty arises in maintenance.
Detection of an anomaly using a vibrational wave has influences of noise from a spindle during rotation of a turn table and noise occurring upon opening/closing of a cover. In order to correct the noise, a necessity arises for processing signals of acceleration, stabilization and deceleration of the turn table with a microcomputer, necessitating a function of complex steps associated circuitry. Even with such a circuitry function including steps adopted, however, the vibration sensor collects noise as a matter of fact.
As described above, in a case where a prior art acoustic sensor or a prior art vibration sensor was employed, precision in error detection during processing for a substrate decreased due to inevitable detection of various kinds of noise and in addition, a necessity arose for a function of complex steps associated circuitry in order to correct noise, resulting in a problem of difficulty in error detection control.